#define RANGE 60001
int singleNumber(int* nums, int numsSize)
{
        int buffer[RANGE] = {0};
    for(int i = 0;i<numsSize;i++){
        nums[i] = nums[i]+30000;
        if(buffer[nums[i]] == 0 ||buffer[nums[i]] == 1) buffer[nums[i]]++;
    }
    for(int j = 0;j<RANGE;j++){
        if(buffer[j] == 1) return j-30000; 
    }
    return -1; 
}